This application relates to a shroud for supporting a variable vane for use in a gas turbine engine wherein leakage paths are eliminated.
Gas turbine engines are known and typically include a fan delivering air into a compressor section where the air is compressed and passed into a combustor section. The air is mixed with fuel and ignited and products of this combustion pass downstream over turbine rotors, driving the turbine rotors to rotate.
The turbine rotors, in turn, drive the fan and compressor section. Historically, a turbine rotor drove a low pressure compressor and a fan at a single speed. More recently, a gear reduction has been placed between the turbine driving the fan and this allows the fan to rotate at slower speeds.
Rotating the fan at slower speeds has allowed the diameter of the fan to increase. It is known for the fan to deliver air into a bypass duct, where it becomes propulsion for an associated aircraft and into a core flow to the compressor. The fans which are provided with a gear reduction may have relatively high bypass ratios, or the volume of the air delivered into the bypass duct compared to the volume of air delivered into the compressor.
As the volume of air delivered into the compressor becomes a smaller percentage, it becomes more and more important to utilize the core air efficiently. The compressor and turbine sections are provided with a plurality of rotating blades and vanes spaced between the rows of the blades. The vanes serve to direct and control the flow of air between stages or rows of the blades.
One type of vane is a variable vane. In a variable vane, a vane is positioned to pivot relative to a radial axis taken from a central axis of the engine. An actuator rotates one side of the vane to pivot and an opposed side of the vane is supported for rotation in a shroud. Typically, the actuator is at a radially outer location.
One known type of shroud has two axially spaced shroud axial halves. These come together to provide a plurality of support locations for the radially inner ends of the vanes. Further, in a split case engine, at least two halves of an engine housing are brought together to define the core engine housing. In such assemblies, each shroud axial half must be formed of at least two circumferential segments.
With various thermal challenges on the shroud, the design has moved such that there are several more circumferential segments. The circumferential segments in each axial half have aligned circumferential edges that combine to create additional leakage paths through the shroud.
When air leaks through the leakage path, the efficiency of driving that air over the vanes and the blades is lost.